This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-291295, filed Sep. 25, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head and a perpendicular magnetic recording apparatus.
2. Description of the Related Art
In a computer field, a magnetic disk apparatus has been much utilized as a randomly accessible external storage having a large capacity. Moreover, with expanding utilization, for the magnetic disk apparatus, there has been an increasing demand for a large storage capacity and a high recording density.
As a method of enhancing the recording density of the magnetic disk apparatus, perpendicular magnetic recording has been proposed. In the perpendicular magnetic recording, as compared with longitudinal magnetic recording, a demagnetizing field in a magnetization transition can remarkably be reduced, a magnetization transition width can be narrowed, and high-density recording is realized. Moreover, in order to raise recording and reproducing efficiencies in the perpendicular magnetic recording, and form a steeper magnetization transition, a magnetic disk of a perpendicular double-layer medium having a soft magnetic backing layer disposed under a perpendicular magnetic recording layer has been proposed.
As a conventional perpendicular magnetic recording head for the perpendicular double-layer medium formed by stacking the soft magnetic backing layer and perpendicular magnetic recording layer, a head having the following structure has heretofore been used. The structure includes a trailing pole (main pole) and a leading pole (auxiliary pole) having a large area in an air-bearing surface, which are disposed with a gap, and an exciting coil acting on these poles. In the perpendicular magnetic recording head, a magnetic field generated by the exciting coil is passed through the trailing pole, soft magnetic backing layer and leading pole to form a closed magnetic path, a magnetic flux can be concentrated on the trailing pole, and a recording efficiency can therefore be enhanced.
In Jpn. Pat. Appln. KOKAI Publication No. 10-320720, it is described that the trailing pole is formed by a forward pole and a rearward pole having a magnetic flux density higher than that of the forward pole, a strong magnetic field is generated from the rearward pole and therefore the recording density is enhanced.
However, when a track width is further narrowed and track density is increased in order to enhance the recording density, a sufficient magnetic field cannot be generated from the whole trailing pole, and it is disadvantageously difficult to overwrite recorded magnetization with a satisfactory SN ratio.
An object of the present invention is to provide a perpendicular magnetic recording head capable of overwriting recorded magnetization at a satisfactory SN ratio even when a track width is narrowed and a track density is increased, and to provide a perpendicular magnetic recording apparatus comprising such a perpendicular magnetic recording head.
According to one aspect of the present invention, there is provided a perpendicular magnetic recording head comprising: a leading pole positioned forward along a head traveling direction; a trailing pole positioned backward along the head traveling direction at a gap length g1 from the leading pole, the trailing pole having a length p along the head traveling direction and a length T in a track width direction, and the trailing pole comprising, in an air-bearing surface, a forward pole having a length p2 along the head traveling direction and a rearward pole having a length p1 along the head traveling direction of which saturation magnetic flux density is higher than that of the forward pole; and an exciting coil, wherein the length p of the trailing pole along the head traveling direction is longer than the length T of the trailing pole in the track width direction, the length p is longer than the gap length g1 between the leading pole and the trailing pole, and the length p1 of the rearward pole along the head traveling direction is shorter than the length p2 of the forward pole along the head traveling direction.
According to another aspect of the present invention, there is provided a perpendicular magnetic recording apparatus comprising; a magnetic disk comprising a perpendicular double-layer film of a soft magnetic backing layer and a perpendicular magnetic recording layer; and a perpendicular magnetic recording head comprising a leading pole positioned forward along a head traveling direction, a trailing pole positioned backward along the head traveling direction at a gap length g1 from the leading pole, the trailing pole having a length p along the head traveling direction and a length T in a track width direction, and the trailing pole comprising, in an air-bearing surface, a forward pole having a length p2 along the head traveling direction and a rearward pole having a length p1 along the head traveling direction of which saturation magnetic flux density is higher than that of the forward pole, and an exciting coil, wherein the length p of the trailing pole along the head traveling direction is longer than the length T of the trailing pole in the track width direction, the length p is longer than the gap length g1 between the leading pole and the trailing pole, and the length p1 of the rearward pole along the head traveling direction is shorter than the length p2 of the forward pole along the head traveling direction.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.